1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and a method of manufacturing the LCD device, and particularly to the LCD device having an ultraviolet-curable (UV-curable) sealing member.
2. Description of the Related Art
It has been required to reduce manufacturing cost of LCD devices used as TV monitors and OA monitors. Productivity of LCD panels has been increased because of the following reasons in a process of manufacturing the LCD panel: reduction in tact time; reduction in the number of steps resulting from introduction of a new process; and increase in size of a mother glass substrate used in manufacturing the LCD panel. A so-called one-drop-fill (ODF) process has been adopted as a specific measure to shorten a liquid-crystal-injecting step in a cell manufacturing step in which two panels are assembled. In the ODF process, liquid crystals are previously dropped to the surface of any one of a thin film transistor substrate (TFT substrate) and a counter substrate, and then the two substrates are joined to each other in a vacuum.
In the ODF process, at least a UV-curable sealing member is used to join the TFT substrate and the counter substrate. Since the sealing member is in contact with a liquid crystal material in the ODF process in a state of not being cured, the sealing member needs to have no compatibility with the liquid crystal material. In addition, a light-curable reaction in the sealing member needs to be sufficiently accelerated when a UV light irradiation process is performed on the sealing member, because the following occur when the curing process of the sealing member is not sufficient. Unreacted components having lower molecular weight in the sealing member dissolve into the liquid crystal material so that visible defects or display unevenness occurs over time, and thus display quality is significantly decreased.
Meanwhile, in the ODF process, it is also necessary to keep the radiation intensity lower, for instance, by shortening the time period for UV light irradiation or performing masking to inhibit UV light from being directly irradiated on portions excluding portions to be irradiated on and the periphery thereof. Specifically, it is necessary to prevent organic members (a liquid crystal material, alignment films and a color filter material) except the sealing member from being deteriorated with light and being dissolved when the curing process is performed to the sealing member by UV irradiation. The prevention is necessary because deterioration of the image quality of the LCD directly results from the change in composition of the liquid crystal material and the alignment films, the change being caused since the liquid crystal material and the alignment films are deteriorated with light and dissolved. Even if display regions are masked during the curing process is performed to the sealing member, UV light partly reflects and scatters in the substrate, and thus cannot be prevented from reaching the display regions. For the reasons, an essential problem is how efficiently UV light is irradiated on a sealing member in the process of curing the sealing member with UV light.
In order to solve the problem, the following LCD device has been proposed. In the LCD device, a counter substrate and a TFT substrate are joined to each other with a UV-curable sealing member mixed with spacers. The LCD device has a configuration in which a reflective layer for UV light source is provided near a main seal pattern on the substrate facing the substrate on which UV light is made incident. The provision is aimed at efficiently and evenly perform the curing process to the main seal with UV light.
However, the related art described above includes a problem that the provision of the reflective layer for reflecting UV light increases the manufacturing cost. In addition, another problem is included that a metal film having a higher reflectance generally has a lower resistance value, and accordingly the types of a film used as the reflective layer is limited depending on the mode in which the liquid crystals are driven. Another problem is also included that the reflective layer of the related art does not ensure efficient use of UV light because the reflective layer does not repeatedly reflects UV light.